docs: def always_read(self, branches):
          """
          Always read these branches, even when in caching mode. Maybe you have
          caching enabled and there are branches you want to be updated for each
          entry even though you never access them directly. This is useful if you
          are iterating over an input tree and writing to an output tree sharing
          the same TreeBuffer and you want a direct copy of certain branches. If
          you have caching enabled but these branches are not specified here and
          never accessed then they will never be read from disk, so the values of
          branches in memory will remain unchanged.
  
          Parameters
          ----------
          branches : list, tuple
              these branches will always be read from disk for every GetEntry
          """
          if type(branches) not in (list, tuple):
              raise TypeError("branches must be a list or tuple")
          self._always_read = branches